Abstract 12535: The Hemodynamic Response to Exercise in Patients With Obstructive Hypertrophic Cardiomyopathy and the Effect of Metoprolol

Abstract

Introduction: Patients with obstructive hypertrophic cardiomyopathy (HCM) frequently experience advanced heart failure symptoms at low levels of physical activity. The relationship between symptoms and loading conditions during exercise is incompletely understood. Whether standard treatment with beta-blockers affects exercise hemodynamics is unknown. Objectives: The aim of this study was to investigate the invasive hemodynamic response to exercise in moderately symptomatic patients with obstructive HCM, and how treatment with metoprolol affects this response. Method: This double-blinded, placebo-controlled, randomized crossover trial enrolled 28 patients with obstructive HCM and New York Heart Association functional class ≥ II from May 2018 to September 2020. Patients received metoprolol or placebo for two consecutive two-week periods in random order. During each treatment period, patients underwent right-heart catheterization at rest and during exercise. The primary outcome was the difference in pulmonary capillary wedge pressure (ΔPCWP) between peak exercise and rest. Results: There was no treatment effect on Δ PCWP between metoprolol and placebo treatment (21(9) mmHg versus 23(9) mmHg; p = 0.12). When comparing metoprolol to placebo treatment, there was no significant difference in PCWP at rest (15 (6) mmHg versus 13 (5) mmHg; p = 0.06) or at peak exercise (35 (12) mmHg versus 37 (10) mmHg; p = 0.38). At peak exercise, metoprolol treatment was associated with a higher stroke volume (101 (24) ml versus 92 (21) ml; p < 0.01), a 25% lower heart rate (107 (19) beats/min versus 139 (23) beats/min; p < 0.0001), and subsequently a lower cardiac output (10.8 (3.3) L/min versus 12.8 (3.2) L/min; p < 0.0001). Conclusion: Exercise in patients with obstructive HCM is associated with a severe increase in left-sided filling pressures which are not affected by metoprolol treatment. Despite increased stroke volume during metoprolol treatment, cardiac output is reduced at peak exercise.